1. Field of the Invention
The present invention relates to an electrical connector for electrically connecting an electronic package such as a land grid array (LGA) chip with a circuit substrate such as a printed circuit board (PCB), and particularly to a connector having retention posts that securely position the electronic package therein.
2. Description of the Prior Art
Land grid array (LGA) electrical connectors are widely used in the connector industry for electrically connecting LGA chips to printed circuit boards (PCBs) in personal computers (PCs). As described in xe2x80x9cNonlinear Analysis Helps Design LGA Connectorsxe2x80x9d (Connector Specifier, February 2001, pp. 18-20), the LGA connector mainly comprises an insulative housing and a multiplicity of electrical terminals. The housing comprises a multiplicity of terminal passageways defined therein in a generally rectangular array for interferentially receiving corresponding terminals. Due to the very high density of a terminal array that an LGA chip may have, the LGA chip needs to be precisely seated onto the LGA connector to ensure reliable signal transmission between the terminals and the LGA chip. Means for accurately attaching the LGA chip to the LGA connector are disclosed in U.S. Pat. Nos. 5,192,213, 5,199,889, 5,232,372, 5,320,559 and 5,362,241.
Referring to FIG. 5, a conventional LGA connector 6 comprises an insulative housing 60, a multiplicity of terminals 61 received in the housing 60, and a load plate 62 and a cam lever 63 pivotably mounted on two opposite ends of the housing 60. The load plate 62 defines a channel 620 receiving the cam lever 63. To mount an LGA chip (not shown) on the LGA connector 6, the load plate 62 is rotated up until it is perpendicular to the housing 60. The LGA chip is seated in the housing 60, and is loosely engaged with the terminals 61. The load plate 62 is rotated down so that it rests on the LGA chip. The cam lever 63 is rotated down until it engages in the channel 620 of the load plate 62. When the cam lever 63 has reached the end of its travel, the load plate 62 presses the LGA chip into firm engagement with the terminals 61 of the connector 6.
In the above-described assembly process, the load plate 62 presses the LGA chip between two opposite sides of the housing 60 of the connector 6. Generally, a material of the housing 60 is not resilient, and the sides of the housing 60 cannot elastically deform under pressure from the LGA chip. If the LGA chip is wider than a distance between the opposite sides of the housing 60, the housing 60 is liable to break. On the other hand, if the LGA chip is narrower than the distance between the opposite sides of the housing 60, the LGA chip may be poorly positioned relative to the terminals 61. This can adversely affect mechanical and electrical connection between the LGA chip and the connector 6. Furthermore, when the load plate 62 presses the LGA chip to firmly engage with the terminals 61, the housing 60 is liable to break if asymmetrical force is inadvertently applied thereto.
FIG. 6 shows another conventional LGA connector 6xe2x80x2 devised to circumvent the above-described problems. The connector 6xe2x80x2 comprises an insulative housing 60xe2x80x2, and a multiplicity of terminals 61xe2x80x2 received therein. In forming the connector 6xe2x80x2, a carrier strip (not shown) is used. The carrier strip comprises a row of the terminals 61xe2x80x2, and a row of connecting sections (not shown) respectively connecting the terminals 61xe2x80x2 with a main body of the carrier strip. The housing 60xe2x80x2 comprises four raised sidewalls 62xe2x80x2, and a flat base 63xe2x80x2 disposed between the sidewalls 62xe2x80x2, The base 63xe2x80x2 and the sidewalls 62xe2x80x2 cooperatively define a space therebetween for receiving an LGA chip (not shown) therein. The base 63xe2x80x2 defines a multiplicity of terminal passageways 64xe2x80x2 for receiving the terminals 61xe2x80x2 therein. When the LGA chip is seated on the LGA connector 6xe2x80x2, the four sidewalls 62xe2x80x2 can securely engage the LGA chip therebetween.
However, installation of terminals 61xe2x80x2 into those passageways 64 near two of the sidewalls 62xe2x80x2 is problematic. Once the terminals 61xe2x80x2 have been inserted into such passageways 64xe2x80x2, the connecting sections of the carrier strip must be cut from their corresponding terminals 61xe2x80x2, Because the carrier strip is located close to the relevant sidewall 62xe2x80x2, there is insufficient space to manipulate the carrier strip to allow easy cutting off of the connecting sections. Such manipulation is blocked by the sidewall 62, which is liable to sustain damage as a result.
Therefore, a new LGA electrical connector which overcomes the above-mentioned problems is desired.
An object of the present invention is to provide an electrical connector for electrically connecting an electronic package such as an LGA chip with a circuit substrate such as a PCB, whereby the electrical connector can facilitate secure positioning of the electronic package therein.
To achieve the above object, an LGA electrical connector for connecting a land grid array (LGA) chip with a printed circuit board (PCB) includes an insulative housing and a plurality of electrical terminals received in a plurality of passageways defined in the housing. Two cylindrical posts extend upwardly from two diagonally opposite corners of the housing respectively. Two recesses are defined in diagonally opposite corners of a bottom surface of the LGA chip respectively, corresponding to the posts. In assembly of the LGA connector with the LGA chip, the LGA chip is inserted into the LGA connector along a direction of assembly. The recesses interferentially receive the posts. Thus the LGA chip is securely mounted on the housing of the LGA connector. The posts of the LGA connector and the recesses of the LGA chip cooperate to precisely position the LGA chip on the LGA connector. This ensures that engagement between contact pads of the LGA chip and the terminals is highly accurate and reliable. In addition, the posts are sized differently from each other, and the recesses are correspondingly sized differently from each other. Accordingly, mismating of the LGA chip with the LGA connector is prevented.